How to filter data in for loop based on external vector

I'm trying to create for loop based on external vector and my expectation is to create aa_loop which is prefiltered based on uni input (for test only). Why below code doesn't produce aa_loop or how to do it in a proper way?

names = ["Sally", "Bob", "Alice", "Hank"]
grades = [1, 5, 8.5, 4]
aaa = DataFrame(name=names, grades=grades)

#for test only
uni = "Bob"

for nm in uni
    aa_loop = subset(aaa,  :name => ByRow(==(nm)))
end

Iterating over a string produces characters, so for nm in uni will produce 'B', then 'o' and then 'b'. Try putting uni in a container, like for nm in (uni,) or for nm in [uni]